Evolution of the fraction of global infection with a non-linear trade-off.

<p>(a) A linear trade-off between the degree of global infection <i>G</i> (horizontal axis) and that of local infection <i>L</i> (vertical axis) assumed so far (dashed curve), and a non-linear trade-off examined here (solid curve), where the local infection decreases in proportional to . (b) Pairwise invasibility plot with <i>x</i>_<i>C</i> = 0.5, <i>p</i>_<i>CC</i> = 0.4, <i>α</i> = 1, <i>β</i>_<i>G</i> = <i>β</i>_<i>L</i> = 10. The black region shows that a mutant strain can invade the resident population, indicating that the evolutionary singular point around <i>G</i> = 0.4 is an evolutionary repeller. (c) Examples of evolutionary trajectory for the mean degree of global infection observed in Monte Carlo simulations starting from two different initial mean values of <i>G</i>(<i>G</i> = 0.3 and <i>G</i> = 0.5).